Photographic emulsion



Patenied Mar. 3%, i942 4 4 2,275,727 rno'rooimrmo sMoLsroN Burt H.Carroll and Charles F. E. Allen, Rochester, N. Y., assignors to EastmanKodak Com- 4 pany, Rochester, N. Y., a corporation of New Jersey NoDrawing. Application February 29, 1940, Serial No. 321,592

17 Claims. '(CI. 95- 7) This invention relates to photographic emulsionsand more, particularly to photographic emulsions of the silver halidetype.

It is known that'the inherent sensitivity of photographic silver halideemulsions (whether spectrally sensitized or not) can be enhanced, andthere has been a constant effort to produce higher speeds inphotographic emulsions. For example, it is known that the speed ofge1atinosilver-halide emulsions can be enhanced by an extended digestionor ripening of the emulsion. It is also known that the speed of silverhalide emulsions (spectrally sensitized or not) can be enhanced byincorporating in the emulsions compounds containinga divalent atoinofthe sulfur group directly joined by a double bond to a single metalloidatom to which is attached at least another group of atoms. Examples ofsuch compounds are allylisothiocyanate and allylthiourea.

We have now found that the speed of photographic silver halide emulsionscan be increased by incorporating in the emulsions (spectrallysensitized or not), surface active substances, such as aqueousdispersing or wetting agents, for example, of the cationic sulfoniumsalt type. (Surface active substances are classified as anionic andcationic, or non-ionic, depending upon whether or not the substancesionize, and if so, depending upon whether the anion or the cation issurface active. Surface active materials are sometimes referred to ascapillary active materials, lipophylic materials or materials whichpossess interface modifying properties.)

Our new method of sensitizing emulsions is an improvement over the knownmethods of enhancing sensitivity, since the speed increases attained byour new method are complementary to the speed increases that can beattained by the prior methods.

The surface active substances act on the emulsion in unknown manner toincrease its effective sensitivity. As a result, the sensitivity isincreased by about the same amount at any wavelength within the range ofits spectral sensitivity, although in spectrally sensitized emulsionsthere is frequently observed an appreciable increase in relativesensitivity for longer wavelengths. Inasmuch as the silver ion andhydrogen ion concentration in our emulsions appear to undergo little orno change by virtue of the presence of the surface active substances, weshall refer to the action of the surface active substances as a kind ofsupersensitization, and we shall refer to mixtures of the surface activesubstances and spectral (optical) sensitizers as combinations, althoughwe donot intend to imply that the surface active substance and thespectral sensitizer are chemically combined.

Our new supersensitized emulsion are an improvement over supersensitizedemulsions known in the .art. The increases in sensitivity which can beobtained with supersensitizing combinations of dyes can be enhanced byour new method. Furthermore, whereas with supersentizing combinations ofsensitizing dyes (see U. S. Patents 2,075,046, 2,075,047 and 2,075,048,each dated March 30, 1937), the supersensitizing effect is confined moreor less to a single spectral region, the sensitization attained in ournew emulsions extends throughout the entire region in which the spectralsensitizer acts (and is fairly uniform in degree throughout the entireregion), while at the same time the sensitivity in the violet and blueregion (where the spectral sensitizer does not act) is also enhanced toabout the same degree.

An object of our invention, therefore, is to provide new photographicemulsions. A further object is to provide emulsions sensitized with asupersensitizing combination of a sensitizing dye and a surface activematerial of the cationic sulfonium salt type. A further object is toprovide a process for preparing such emulsions. 1

According to our invention, we incorporate in a photographic silverhalide emulsion, a cationic surface active sulfonium salt substance. Thesurface active substance can be incorporated in any suitable form, e. g.in the form of a solution in a suitable solvent, such as water or methylalcohol. The surface active material should be thoroughly incorporatedin the emulsion. The surface active material can be added to thefinished emulsion, or at any stage of the preparation of the emulsion.

In the case of spectrally sensitized emulsions, the surface activesubstance can be incorporated in the emulsion before, simultaneouslywith, or after the sensitizing dye, although in some cases, ashereinafter set forth, it is advantageous to incorporate the sensitizingdye before incorporating the surface active substance. The methods ofincorporating sensitizing dyes in emulsions are, of course, well knownto those skilled in the art. Ordinarily, it is advantageous to employ asolution of the sensitizing dye in a suitable solvent, e. g. methylalcohol. Ethyl alcohol or acetone may be employed in cases where thesolubility of the sensitizing dye in methyl alcohol is very low.

Sensitizing dyes are ordinarily incorporated in the washed, finishedemulsions, and, in accordance with our invention, the surface activesubstances are also advantageously incorporated in the washed, finishedemulsions. However, the

surface active substance can be added to the emulsion during thepreparation thereof, i. e. during the precipitation, the firstdigestion, or the second digestion (the ripening). After preparing theemulsions in the presence of the surface active substance, thesensitizing dyes can be incorporated in the so-prepared emulsions.

As cationic sulfonium salt surface active substances, we have found thatthose which do not contain a hydrogen atom on the sulfonium sulfur atom(i. e. the so-called ternary sulfonium types) are advantageouslyemployed. We have found that the sulfonium cation advantageously shouldcontain at least one organic group containing a chain of at least eightmembers. Advantageously, such members are from the group consisting ofcarbon, oxygen, nitrogen and sulfur atoms. One or more aromatic rings,such as a benzene ring, for example, can take the place of one or moreof the eight or more atoms. Thus, a

benzene ring can take the place of one atom, while a naphthalene ring(two benzene rings fused together) can take the place of two atoms. Theatoms attached to the eight or more atoms in the chain (where valencepermits) can be hydrogen, oxygen, sulfur, carbon or halogen, forexample. Any aromatic ring system in the chain can carry simplesubstituents. We have found that cationic sulfonium salt surface activesubstances having a sulfonium cation containing a lipophylic organicgroup which contains a chain composed of from nine to twelve membersselected from the group consisting of carbon atoms, oxygen atoms, sulfuratoms and aromatic ring systems are advantageously employed.

The anion may be any acid radical, such as chloride, bromide, iodide,p-toluenesulfonate, perchlorate or alkylsulfate, for example. Of course,introduction of halide anions into photographic silver halide emulsionsalters the halide concentration in the emulsion and compensating changesin the emulsion may be desirable, if such sulfonium salts are employed.For this reason, we ordinarily prefer to employ surface activesubstances containing anions other than halides. Perchlorates andp-toluenesulfonates are advantageously employed.

The following are representative of organic lipophylic groups containinga chain of at least eight members selected from the group consisting ofcarbon atoms, oxygen atoms, sulfur atoms and aromatic ring systems:

Nonyl, CHa(CH2) a- (nine atom chain) Decyl, CH3--(GH2)9- (ten atomchain) Lauryl, CHs(CI-I2) 11 (twelve atom chain) Cetyl, CHs-(CHz) 15-(sixteen atom chain) Heptoxymethyl, CHs-(CHz) s-OCH2 (nine atom chain)Undecoxymethyl, CH3(CH2)1 -OCH2 (thirteen atom chain) Heptylthiomethyl,CH3-(CH2) aSCH2- (nine atom chain) Carbnonoxymethyl,

(nine atom chain) Butoxyethoxyethyl, CHa-(CHz) aO(CH2) 2- OCH2-CHz- (tenatom chain) Ter-butylphenoxyethoxyethyl CH cm-e o-cm-cm-o-cn,-om

i CH:

(eight atom-i-phenyl group chain) Formylphenyioxyethoxyethyl (sevenatom+phenyi group chain) Phenylphenoxyethoxyethyl (six atom-i-two phenylgroups chain) Methylphenoxypropoxypropyl (nine atom+phenyl group chain)3,7-dimethyloctanoxymethyl cm-o HcH,-cHr-ca,-cu-careas-042mm In I (tonatom chain) Citronelloxymethyl C HFCH-C Hr-CH:C Hz-CH-CEr-CH-O-Cliz- HaHa (ten atom chain) (Alcohol radicals in commercial oil of sandal-W0Od)-OCH2 (at least ten atom chain) w-Hydroxydecyl HOCH2-(CH2) a-CHz-(eleven atom chain) p-Naphthoxyethoxyethyl O-CHz-CHz-O-CTh-Cllr (sixatom two phenyl group chain) advantageous concentration was found to bebetween about 20 mg. and about 200 mg. of the 55 surface activesubstance per gram-mole of silver halide in the emulsion, althoughgreater or smaller concentrations can be employed. We have found thatexcesses of the surface active substance are advantageously avoided,since excesses 60 produce fog in the emulsions. For surface activesubstances containing a lipophylic group containing a chain of eight toten members, we have found that as much as about 400 mg. of surfaceactive substance per gram-mole of silver halide in the emulsion canordinarily be employed without encountering excessive fog, while withsurface active substances containing a lipophylic group containing achain of eleven to 12 or more members, we have found that not more thanabout 200 mg. of surface active substance per gram-mole of silver halideshould ordinarily be employed.

The optimum range of concentration for any particular surface activesubstance described herein is ordinarily fairly narrow and can bestaerator:

be determined by employing a series of concentrations of the surfaceactive substances, separately in several batches of the same emulsionand determining the sensitivity of the several batches before and afterincorporation of the surface active substance, in the usual manner,which is, of course, well known to those skilled in the art. Briefly,the method of determining sensitivity of emulsions comprises coating theemulsion onto a glass plate to a suitable thickness and drying (thecoated emulsion and then testing the resulting photographic plate in awedge spectrograph and a sensitometer, whereby spectral sensitivity andspeed of the emulsion on the plate is determined.

When employing spectrally sensitized emulsions, the spectral sensitizers(sensitizing dyes) are advantageously employed in about their optimumconcentration, which ordinarily lies between about 3 mg. and mg. ofspectral sensitizer per liter of emulsion containing about 0.25 grammoleof silver halide, although concentrations above or below the optimumconcentration can be employed. With fine-grain emulsions, which includesmost of the ordinarily employed silver chloride emulsions, the ratio ofconcentration of sensitizing dye to the concentration of silver halidein the emulsion is advantageously larger than in the coarser grainemulsions where smaller amounts of sensitizing dyes usually give optimumsensitization. The optimum concentration, as above referred to, of asensitizing dye (i. e. the concentration at which greatest sensitivityoccurs) can be readily determined in a manner well known to thoseskilled in the art by measuring the sensitivity of a series of emulsionscontaining diiferent concentrations of the sensitizing dye.

Our invention is directed particularly to the silver halidedeveloping-out emulsions customarily employed in the art, including thegelatino-silverchloride, the gelatino-silver-bromide and thegelatino-silver-bromiodide developing-out emulsions, for example.However, our invention can be employed with silver halide emulsionswherein the carrier is other than gelatin, for example, a resinous orcellulosic derivative substance which has substantially no deleteriouseffect on the light-sensitive materials in the emulsions.

As spectral sensitizers (sensitizing dyes) only those which arenon-acidic can be employed in practicing our invention. sensitizingdyes, such as Congo red, which disperse in water to give a coloredanion, i. e. acidic sensitizing dyes, appear to interfere with thesurface active agent, with the result that neither the acid dye nor thesurface active substance exert a substantially beneficial effect on theemulsion. As non-acidic sensitizing dyes, we include all the knownneutral and basic sensitizing dyes, i. e. those sensitizing dyes whichdo not give colored anions. Some 01 these non-acidic sensitizing dyes,such as the cyanine dyes, give colored cations. Exemplary of thenon-acidic sensitizing dyes are the sensitizing cyanine dyes, (see, forexample, United States Patents 1,846,300; 1,846,301; 1,846,302;1,846,303 and 1,846,304, each dated February 23, 1932, United StatesPatent 1,861,836, dated June 7, 1932, United States Patent 1,939,201,dated December 12, 1933, United States Patent 1,942,854, dated January9, 1934, United States Patent 1,957,869, dated May 8, 1934, UnitedStates Patent 1,962,124, dated June 12, 1934, United States Patent1,969,446, dated August 7, 1934,

I emulsions prepared in oi incorporating 11, 1934; United States ?atent1,990,507, dated February 12, 1935, United States Patent 2,094,580,dated October 5, 1937, United States Patent 2,112,140, dated March 22,1938 and. French Patent 757,813, published January 5, 1934), the

sensitizing merocyanine dyes, (see United States Patent 2,078,233, datedApril 27, 1937,'United States Patent 2,089,729, dated August 10, 1937,United States Patent 2,153,169, dated Aprfl 4, 1939 and United StatesPatents 2,177,401, 2,177,402, and 2,177,403, dated October 24, 1939),the sensitizing hemi-cyanine dyes, (see-United States Patent 2,166,736,dated July 18, 1939) and the sensitizing hemioxonol dyes, (see UnitedStates Patent 2,165,339, dated July 11, 1939 and French Patent 841,632,published May 24, 1939). e the process of our invention is subject tovariation, particularly as respects the nature and quantity of surfaceactive substance employed, the nature and quantity of the spectralsensitizer employed, it any, the nature of the silver halide emulsionemployed, and the manner the surface'active substance and the spectralsensitizer (if any) in the emulsions, the following example will serveto illustrate the manner of obtaining our new emulsions. This example isnot intended to limit our invention.

, Example 1 Into one liter of fiowable, washed, finishedgelatino-silver-bromide developing-out emulsion containing about 0.25gram-moles of silver halide were incorporated slowly,with stirring, amethyl alcoholic solution of 2,2'-dimethyl-8-methyl-3,4,3',4'-dibenzothiacarbocyanine chloride. Suflicient of the alcoholicsolution was added to incorporate about 15 mg. of the 'carbocyaninechloride in the emulsion.

To the resulting emulsion were added slowly and with stirring, a 1% (byweight) aqueous solution or lauryldimethyl-sulfonium-p-toluenesulfonate.Sufiicienhot the aqueous solution was added to incorporate about 50 mg.of the ptoluenesulfonate in the emulsion.

Photographic elements can be made from coating the emulsions to asuitable thickness on a suitable support and drying the coated emulsionin a manner well known to those skilled in the art. Suitable supportsare, of course, glass, photographic paper support, and photographic filmsupport. The photographic film support may, of course, be of celluloseacetate, cellulose nitrate or any other suitable cellulose derivativeand be 01' any suitable resinous material, such as polyvinyl acetalresin, for example. Our new emulsions are advantageously coated on glasssupport.

Example 2 Nonyldi'methylsulfonium p toluenesulfonate was the specificsalt employed as the addition agent in this example. This salt wasincorporatedinto a sensitized emulsion by procedure comparable to thatalready described. The nonyldimethylsulfonium p-toluenesulfonate wasadded in an amount between 20-100 mg. per liter of emulsion. Thiscompound appeared to exhibit very little tendency to cause fog andconsequently high concentrations may be employed.

Example 3 In this example bis (laurylmethylsulfonium ptoluenesulfonate')diacetyl was the specific agent the above manner by.

tized emulsion by procedure comparable to that already described.Comparable proportions were employed and a sensitivity increase of inthe neighborhood of 50% was obtained when the resultant emulsion wascoated on glass or film base.

The following table contains a summary of some of the more practicalresults obtained according to the instant invention. In thistable thecontrol referred to is the emulsion without the sulfonium salt. In someinstances, as in Table II, the control, as indicated, contains asensitizing dye. The controls, of course, were processed and otherwisehandled in exactly the same manner as the emulsions containing thesulfonium salts.

TABLE I.Undyed geZatz'no-siloer-bromiodide emulsion f g CompositionSpeed 7 Fog 59 Control 560 0.54 .05 00. n-Nonyl dimethyl suli'o- 6450.55 .04

nium p-toluenc suliouate, 20 mg./liter.

TABLE II.-Sulfomum compounds 21:. dye-sensitizedgelatino-szlver-bromzodlde emulsion No. 12 White (minus light blue)Illusexposure filter tration Composition Fog exp.

l0/i l0/i speed 7 speed 7 G1 (Control) 2,2-dimethyl- 525 0.61 .07 1320.62

8 ethyl thiacarbocyanine bromide, 15 mg./liter. 71 n-Nonyl dimethyl sul-605 0.70 .08 190 0.62

fouium p-Toluene sulfonate, 30 rug/liter. 72 n-Nonyl dimethyl sul- 6900.78 .08 220 0.76

iouium p-Toiuene suliouate 100 mg./llter. 73 u-Octyl dimcthyl sul- 6450.78 .08 250 0.61

ionium p-Toluene sulionate 100 tug/liter. 74.. n-Decyl dimethyl sul- 8300.75 .09 200 0.75

ionium p-Toluene sulionate 50 mg./liter. 75 (Control) l-ethyl-2- 4900.69 .05 37 0.76

methyl thia-2'-eyanine iodide 20 mg./liter. 76 n-Nonyl-dimethyl sul- 5500.80 .06 45 0.86

ionium-p-toluene sulfonate 50 mg./l1ter. 67 (Control) 2-dipheuyla- 4550.82 .06 126 0.83

miuo-5(2-ethyl-l-benzothiazylidene ethylidene)-4-(5)-th1azolone, l5mg./liter. 77 n-Nonyl di ethyl sul- 630 0.84 .09 235 0.75

fonium p-toluene sulionate50n1g./lite r. 78 (Control) 2[4-(l -p1peri-575 0. 76 .09 205 0.78

dyl)-l,3-butadienyll fl- IBphthlBZ0l7rt ethiode,20m 1 er. 79 n-Nonyl diriethyl sul- 775 0.78 .10 225 0.78

ionium p-toluene sulionate, 50 mgJhter.

tration, it being kept in mind, however, that due regard is had for notexceeding the amounts herein described, depending upon whether long orshort alkyl chain containing compounds are employed and other factors asalready explained.

The sulfonium compound described herein may be obtained from varioussources and by various methods provided the products are of sufficientpurity and otherwise possess qualities rendering them capable of meetingphotographic specifications.

The surface active sulfonium salts may be made by various publishedmethods disclosed in patents and other disclosures (see for exampleUnited States Patent 2,090,890, dated August 24, 1937, and United StatesPatent 2,121,823, dated June 28, 1938). Hence, it is unnecessary todiscuss the preparation of these compounds herein, since such surfaceactive sulfonium salts per se form no part of the present invention.

It is apparent from the foregoing that our invention is susceptible ofsome modification; hence we do not wish to be restricted exceptinginsofar as may be necessitated by the prior art and the spirit of theappended claims.

What we claim as our invention and desire to be secured by LettersPatent of the United States 1. A photographic silver halide emulsionsensitized with a cationic surface active sulfonium salt.

2. A photographic silver halide developing-out emulsion sensitized witha cationic surface active sulfonium salt.

3. A photographic gelatino-silver-halide emulsion sensitized with acationic surface active ternary sulfonium salt.

4. A photographic gelatino-silver-halide developing-out emulsionsensitized with a cationic surface active ternary sulfonium salt.

5. A photographic gelatino-silver-halide developing-out emulsionsensitized with a supersensitizing combination of at least onenon-acidic sensitizing dye together with a cationic surface activesulfonium salt.

6. A photographic silver halide emulsion sensitized with a cationicsurface active ternary sulfonium salt.

'7. A photographic silver halide developing-out emulsion sensitized witha cationic surface'active ternary sulfonium salt.

8. A photographic silver halide developing-out emulsion sensitized witha supersensitizing combination of at least one non-acidic sensitizingdye together with a cationic surface active ternary sulfonium' salt.

9. A photographic gelatino-silver-halide emulsion sensitized with asupersensitizing combination of at least one non-acidic sensitizing dyetogether with a cationic surface active ternary sulfonium salt.

10. A photographic gelatino-silver-halide developing-out emulsionsensitized with a supersensitizing combination of a non-acidicsensitizing dye together with a surface active ternary sulfonium salt,the cation of which contains at least one organic group containing achain of at least eight members selected from the group consisting ofcarbon atoms, oxygen atoms, sulfur atoms, nitrogen atoms and benzenenuclei.

11. A photographic gelatino-silver-halide developing-out emulsionsensitized with a supersensitizing combination of a non-acidicsensitizing dye together with a surface active ternary sulfonium salt,the cation of which contains at least one organic group containing achain of from nine to twelve members selected from the group consistingof carbon atoms, oxygen atoms,

grams per gram-mole of silver halide in the emulsion a cationic surfaceactive ternary sulfonium salt, the cation of which contains at least oneorganic group containing a chain of from 9 to 10 members selected fromthe group consisting of carbon atoms, sulfur atoms, oxygen atoms,nitrogen atoms and benzene nuclei.

13. A photographic gelatino-silver-halide developing-out emulsionsensitized with a non-acidic sensitizing dyeland containing, in aconcentration of from about 20 to about 200 milligrams per gram-mole ofsilver halide in the emulsion, a cationic surface active ternarysulfonium salt, the cation of which contains at least one organic groupcontaining a chain of from 11 to 12 members selected from the groupconsisting of carbon atoms, nitrogen atoms, oxygen atoms, sulfur atomsand benzene nuclei.

14. A photographic gelatino-silver-halide developing-out emulsion,sensitized with a nonacidic sensitizing dye and containing, in aconcentration of from about 20 to about 200 milligrams per gram-mole ofsilver halide in the emulsion, a cationic surface active ternarysulfonium salt, the cation of which contains at least one organic groupcontaining a chain of from 9 to '10 members selected from the groupconsisting of carbon atoms, sulfur atoms, oxygen atoms, nitrogen atomsand benzene nuclei.

'15. A photographic gelatino-silver-halide de veloping-out emulsion,sensitized with a nonacidic sensitizing dye and containing, in aconcentration of from about 20 to about 200 milligrams per gram-mole ofsilver halide in the emulsion, a cationic surface active n-nonyldimethyl sulfonium salt.

16. A photographic gelatino-silver-halide developing-out emulsion,sensitized with a nonacidicsensitizing dye and containing, in aconcentration of from about 20 to about 200 milligrams per gram-mole ofsilver halide in the emulsion, acationic surface active n-decyl dimethylsulfonium salt.

17. A photographic geZatino-silver-halide developing-out emulsion,sensitized with a nonacidic sensitizing dye and containing, in aconcentration of from about '20 to about 200 milligrams per gram-mole ofsilver halide in the emulsion, a cationic surface active n-octyldimethyl sulfonium salt.

BURT H. CARROLL. CHARLES F. H. ALLEN.

